CHAPTER 4: COMMUNICATIONS
MODBUS COMMUNICATIONS
EPM 4
5
00 SUB METER – INSTRUCTION MANUAL
4–3
4.1.5
Modbus Data Register (R4 Type) Groups
The EPM4
5
00 has divided the supported register map (see following pages) into the
following register groups for various fixed and dynamic data values:
• Setup Information
• Interval
• Average Interval Data
• Instantaneous Data
• Three-Phase Data
• Real Time Data
• Meter Configuration Data
The EPM4
5
00 provides access to stored-interval data channels via Modbus command. The
data items as defined in the following register map are based on default data channels
that include the following 3-phase-totaled values (interval average) per meter:
• Real Power in kW
• Reactive Power in kvar
• Apparent Power in kVA
• Power Factor
Data is logged per the configurable time interval value. The default log interval is 15
minutes.
The Modbus master can request stored interval data by writing the interval date and time
to the appropriate registers and by setting the data status register to 1. Upon the data
ready flag (address 67) being written to 1, the interval data registers (addresses 100 to 107)
are simultaneously updated with the appropriate values for the requested interval. The
data ready flag returns a 0 for “data is ready”, or “2” for “invalid time interval requested.”
The EPM4
5
00 also provides registers that constantly hold the oldest stored-interval
(addresses 58 to 60) and most recent stored-interval time and date stamps (addresses 61
to 63).
4.1.6
Instantaneous Data Items
The EPM4
5
00 provides registers for per-phase instantaneous values (see below).
Instantaneous register values are updated once per second.
• Frequency
• Total Harmonic Distortion (% for volts)
• Voltage
• Current
• Real Power in kW
• Reactive Power in kvar
• Apparent Power in kVA
The EPM4
5
00 provides one-second updated inputs, including the following 3-phase-
totaled values per 3-phase-meter:
• Energy: kWh and kvarh
